ATM transmission system

ABSTRACT

The invention discloses means and methods for transmission of information in paths of an ATM network wherein a path setup for at least one new path in the network is initiated if the path capacity currently used for transmission of information exceeds a threshold, wherein a path release for at least one path in the network is initiated if the path capacity currently used for transmission of information is below a threshold.

[0001] AAL type 2 switching as a resource saving variant of ATM basedswitching methods requires virtual channel connections (VCC, in thefollowing called ‘AAL type 2 path’ or simply ‘path’.) as bearers of AALtype 2 connections. The AAL type 2 paths may be provided as permanentpaths (PVC VCC), or as switched paths (SVC VCC), or as soft PVC VCC. Itis an object of the invention to enable network elements to set up SVCpaths in a flexible, dynamical and anticipatory way according to thetraffic volume carried by the network, and to release SVC paths when thetraffic volume is decreasing.

[0002] Known solutions exclusively use PVCs as paths. There are nosolution providers or publications known which are using, or do intendto use SVCs as paths.

[0003] It is an object of the invention to enable network elements toset up SVC-paths in a flexible, dynamic and anticipatory way in anetwork according to the traffic volume, and to release SVC-paths againwhen traffic volume is decreasing. The object is achieved by theinvention as set forth in the claims and the description.

[0004] The setup and release of paths is controlled by access resourcemanagement. An important element of resource management is a mechanism,which uses (administrable or preset) threshold values to recognize,whether the currently available path capacity is sufficient, or whetherthe path capacity is too high. The verification of the path capacity isperformed each time when resources (bandwidth, AAL type 2 channels) arerequested for the setup of an AAL type 2 connection (‘call by call’), orwhen AAL type 2 connection resources are to be released. Depending onthe result of the verification, resource management initiates the setupof a new path, releases an unused path, or decides to leave the pathconfiguration as it is. The functions necessary to setup and release apath are performed by switching components, especially provided for thistask, and using a suitable signalling. Those switching components, andalso other intermediate switching components involved in the setup ofcalls, may use network-learned routing information (that is exchanged bya suitable protocol) or administered routing information for the setupof new paths. Moreover, such routing information may also be used bythose switching components when choosing a path to be released.

[0005] One advantage of such a solution is the reduction ofadministrative efforts to be provided by a network operator. Anotheradvantage is the adaption of ATM based virtual transmission paths to thecurrent traffic volume, automatically controlled by the network workelement. The invention allows to just in time provide those AAL type 2transmission paths, which are currently needed to process the AAL type 2traffic without interferring with that traffic.

[0006] The following description of embodiments of the invention and theenclosed figures disclose further possible features and advantages ofthe invention.

Dynamical AAL Type 2 Path Switching

[0007] 0.1 List of figures and tables

[0008]FIG. 1: Connection control elements

[0009]FIG. 2: AM data structures

[0010]FIG. 3: Path reservation

[0011]FIG. 4: Connecting A2SC and LIC

[0012]FIG. 5: Disconnecting A2SC and LIC

[0013]FIG. 6: Traffic flow

[0014]FIG. 7: Message parameters

[0015]FIG. 8: Path setup at the originating endpoint

[0016]FIG. 9: Path setup at the destination endpoint

[0017]FIG. 10: Path release at the originating endpoint

[0018]FIG. 11: Path release at the destination endpoint

[0019] 0.2 Abbreviations A AAL ATM Adaption Layer AESA ATM End SystemAddress AINI ATM Internetwork Interface AM Access Manager ATMAsynchronous Transfer Mode ATMF ATM Forum A2C AAL type 2 Channel A2SCAAL type 2 Server Card B BCF Bearer Control Function C CAM CallMaintenance CIH Connection Identifier Handler CRA Connection ResourceAgent CRH Connection Resource Handler D DBMS Data Base Management SystemDSS2 Digital Subscriber Signalling #2 E EP Endpoint ESIS EnhancedSignalling Interworking Subsystem F FIFO First in first out I IEInformation Element ISDN Integrated Services Digital network ISUP ISDNUser Part ITU International Telecommunications Union L LC Leg ControllerLH Leg Handler LIC Line Interface Card N NNI Network to NetworkInterface NRM Network Routing Manager P PNNI Private Network NodeInterface PRH Protocol Handler PVC Permanent Virtual Channel R RHSResoure Handler Subsystem RNC Radio Network Controller S SAG SignallingAgent SLT Signalling Link Termination SVC Switched Virtual ConnectionSVP Switched Virtual Path T TRAU Transcoding and Rate Adaption Unit TSCTRAU Server Card U UNI User to Network Interface V VC Virtual ChannelVCC Virtual Channel Connection VCI Virtual Channel identifier VP VirtualPath VPC Virtual Path Connection VPCI Virtual Path Connection IdentifierVPI Virtual path identifier

[0020] 0.3 Overview

[0021] AAL type 2 switching depends on virtual channel connections (VCC)as bearers of AAL type 2 connections. The VCCs may be represented bypermanent VCCs (PVC), by switched VCCs (SVC), or by switched PVCs (alsocalled soft PVCs). The description puts its focus on SVCs. If soft PVCimplementation is desired, the ability to switch

[0022] virtual channels is a prerequisite. The advantage of usingswitched virtual channels rather than PVCs obviously is a reduction ofadministrative efforts. An operator is not forced to initially build upPVCs within the network, and to continously measure the traffic for thepurpose of keeping PVC path resources up to date. The networkdynamically and automatically establishes the AAL type 2 paths asrequired by the traffic flows through it.

[0023] Mixed operation shall however be supported. Operators of smallnetworks may prefer the PVC solution. Others may decide to use PVCstowards the access side (connecting RNCs), but are favouring SVCsmeshing the network.

[0024] 0.4 Signalling

[0025] Consulting the standards, ITU-T amendments to Q.2931 defineadditional information elements or extensions to existing ones such asthe AAL parameters IE or the generic transport identifier IE to supportAAL type 2 switching using SVCs.

[0026] ATMF papers clearly suggest DSS2 signalling protocols, such asUNI signalling 4.0 (which may be considered identical to Q.2931), orAINI and PNNI.

[0027] AINI signalling has been developed by the standardization bodiesfor inter-network communication, especially between PNNI and non-PNNInetworks. Since nobody talks about ISUP in the context of SVC pathes forAAL type 2 switching, the recommendation (and furthermore more theworking assumption) is to implement UNI and AINI signalling.

[0028] So far there are no standards existing which specify theprocedures to be used when setting up or releasing AAL type 2 pathsbased on SVCs.

[0029] 0.5 Connection Control Architecture

[0030] (FIG. 1: Connection Control Elements)

[0031] The centrally located connection control functions comprise theAAL type 2 connection processing (AAL2 control) and the SVC connectionprocessing (SVC control). The SVC connections represent the paths of AALtype 2 connections.

[0032] The signalling agent (SAG) and the related signalling linkterminations (SLT) interface to AAL2 control, whereas ESIS and itsprotocol handler (PrH) will serve SVC control.

[0033] The interfaces to the access manager (AM) and network routingmanager (NRM) are common to both AAL2 and SVC control.

[0034] Towards the periphery, AAL2 control interfaces with theconnection identifier handler (CIH), which in turn handles the switchingrequests to the server cards TSC and A2SC, whereas switching requestsfrom SVC control take the path via the resource handler (RHS) towardsA2SC and LIC. Alternatively CIH and RHS may be merged to a connectionresource handler (CRH), commonly holding the interface to connectioncontrol and to the peripheral units.

[0035] SVC control has no interface with call control. The bearercontrol function (BCF) of a served user communicates with AAL2 controlonly.

[0036] There will be no direct interface between SVC and AAL2 control,for example via a message interface. The coupling is indirect via AM,which indeed decides when to set up or release an AAL type 2 path.

[0037] 0.6 The Access Manager

[0038] 0.6.1 Access Data Structures

[0039] The access manager AM plays a central part in the AAL type 2 pathswitching mechanism. AM is dedicated to allocate and release resourcesfor the setup and release of AAL type 2 connections carried by PVC andSVC paths, as well as to allocate and release resources for the setupand release of SVC connections as the the paths of AAL type 2connections.

[0040] As a DBMS download unit, AM manages download data and transientdata of accesses, virtual path connections (VPC, in the traditional ATMcontext), virtual channels (VC, switched or permanent), and AAL type 2channels. This makes AM the overall access related resource holder, andputs it into a position to most efficiently decide, when AAL2 paths needto be setup or released.

[0041] The figure below shows 4 hierarchical data object levels,beginning with accesses via virtual path connections and virtual channelconnections (the AAL type 2 paths), down to the AAL type 2 channels. Itis not intended here to give a complete data model. A fewcharacteristics, as far as AAL type 2 path switching is concerned, shallhowever be highlighted.

[0042] From the viewpoint of SVC control, an access can be a UNI or anNNI (AINI) access. Threshold values, as needed for opportune path setupor release, could be attached to accesses or, alternatively, to VPCs.

[0043] Due to AAL type 2 path switching, the data object level ‘VPC’ isintroduced. VPCs, like in classical ATM switching, may carry attributessuch as traffic type (e.g. constant bit rate), maximum of allowed peakcell rates, SVC selection methods, or AAL type 2 traffic type (voice,data). Accumulated cell rates of active virtual channels are at leastrequired as part of the transient data. Switched VCCs do not havedownload data. Accumulated traffic data such as currently used cellrates or the number of active AAL type 2 channels need to be kept astransient data.

[0044] The third data type (lists, as indicated in the figure) comprisesmembers of a data object. The term ‘list’ is to be understood in acommon sense. The implemented data structures shall ensure that memberscan be searched, added, and deleted by use of their identifiers withinefficient time.

[0045] (FIG. 2: AM Data Structures)

[0046] 0.6.2 Path Selection

[0047] As a minimum requirement, the forward and backward sequential SVCassignment method shall be implemented. It is recommended, to implementa forward and backward circular assignment as well. Optionally, one mayconsider FIFO queuing mechanisms.

[0048] 0.6.3 Path Monitoring

[0049] The decision when to initiate a new path setup or path release ismade by AM on a per call base, that is, whenever AM is called by AAL2control to allocate or deallocate resources for an AAL type 2 connectionsetup or release. AM compares the currently consumed path capacity(accumulated cell rates, number of AAL type 2 channels) with giventhreshold values.

[0050] If on allocating resources the threshold value for setup isexceeded, AM selects a new path, and sends a message to SVC control,requesting the setup of the path. SVC control confirmes the completionof path setup. Now AM may assign AAL type 2 channels to the new path.

[0051] Simularly, if upon deallocating the resources of an AAL type 2connection the currently consumed path resources fall below thethreshold value for release, AM requests SVC control to release apreviously reserved, inactive path.

[0052] (FIG. 3: Path Reservation)

[0053] In general, one may tailor a threshold mechanism for the SVCselection method. Referring to the example below, a forward sequentialselection is assumed, and AAL type 2 connections are assigned to thelowest path possible. Hence AM fills up from bottom to top, which makesthe path on top the next candidate for release.

[0054] A threshold mechanism independent of SVC selection methods may beachieved, if one considers the sum of all active path resources, anddefines the threshold values as distances to the available resources ofall active pathes.

[0055] 0. 6. 4 Path Ownership

[0056] Path monitoring as described above is performed by an AM which isallocating resources for an originating AAL2 connection endpoint. Inthis way AM becomes the owner of a path, and indeed may be considered asa user requesting path setup. The path owner eclusively allocates a pathidentifier. An AM verifying the requested AAL type 2 connectionresources at the destination endpoint of a path must assume that thepath owner monitors the path resources. Consequently, only the pathowner may release the path.

[0057] 0.6.5 Exceptional Conditions

[0058] Within normal operation, the threshold mechanism shall ensurethat path resources are provided in advance. There may occur situationshowever, where provision in advance cannot be guaranteed. Whenever a VPCis brought into service (again), triggered by administration or by callmaintenance, there will be no path existing. With the mechanism above,this will be detected when AM needs to assign an AAL type 2 connectionto a path. AM now requests path setup, but for the present must rejectresource allocation to AAL2 control. The problem can be overcome byautomatically establishing a first path within a VPC as soon as AMreceives the indication (from DBMS or possibly CAM) that a VPC isavailable for connection processing.

[0059] Another exceptional situation may occur, when extremely bulkytraffic comes in within a short period of time.

[0060] As a general backup solution with a good chance not to loose thecall, AAL2 control shall reattempt the connection setup after anappropriate delay, whenever it receives a rejection from AM indicating‘no path available, requesting setup’.

[0061] 0.7 Routing

[0062] SVC and AAL2 control commonly use the same routing, ideallyhaving the same routing interface.

[0063] The routing manager shall be able to deliver different routingresult categories, such as ‘local destination’, if the path terminatesin the own network element, or ‘routing destination’, if the path has tobe routed further. The criteria to terminate the path may be based ontranslation of the called party number, or on comparison of the calledparty number with the own network element address.

[0064] 0.8 Alternative Routing Capability Shall be Supported. PathSwitching

[0065] The requests to connect or disconnect pathes are initiated by theleg handlers, and addressed to a connection resource agent (CRA),residing within SVC control.

[0066] (FIG. 4: Connecting A2SC and LIC)

[0067] CRA maps the received information into messages towards theresponsible resource handlers (we will call them CRH), sends themessages, receives the confirmations, and acknowledges to the leghandler (LH).

[0068] The sample figure does not intend to dictate the message flowtowards the periphery. Whether or not a sequentialization is required(as shown in the figure), depends on further analysis studies. Forperformance reasons, parallel tasks should be preferred wheneverpossible. If any coordinative functions are required, they shall be inhands of CRA.

[0069] Coordination (sequentialization) by CRA may be also necessary incases, when the connection setup is aborted due to failures, eitherencountered by SVC control, or signalled by a partner service (AM orESIS). The release procedures of the leg handlers then may request apremature disconnection, although previously issued connect requests arenot yet completed.

[0070] Similar aspects matter when disconnecting a path as shown in thefigure below. Certain path setup scenarios may require an automaticsetup repeat attempt, or an alternative routing attempt. Due toperformance reasons, the outgoing leg (represented by LH and ESISinstance) are released simultaneously to setting up a new leg (with newLH and ESIS instances). Considering the activities towards theperiphery, this means that disconnect requests are likely to be still onthe way, when another connect request arrives at CRA.

[0071] (FIG. 5: Disconnecting A2SC and LIC)

[0072] The figure below shows a (simplified) traffic flow through theATM switching fabrics after having connected LICs to AAL type 2 servercards.

[0073] (FIG. 6: Traffic Flow)

[0074] In the upper left corner, a path, externally identified by VPCI=aand VCI=b, has been switched through the LIC, and terminated on A2SC atendpoint x. The same has been done for an endpoint y, VPCI=c and VCI=d.The arrows are denoting the direction of call setup from the callingparty towards the called party, but not necessarily the direction ofpath setup. This depends on the interface (radio or network interface),and in case of a network interface on the chosen type of forward orbackward bearer establishment.

[0075] The dotted line with the internal endpoints u and v representsthe AAL type 2 sphere of influence, which is not shown in detail here.

[0076] 0.9 Basic Path Setup and Release

[0077] We are now prepared to set up and release SVC pathes. The tablebelow gives a list of parameters used in the message flow charts.

[0078] (FIG. 7: Message Parameters)

[0079] 0.9.1 Path Setup at the Originating Endpoint

[0080] (FIG. 8: Path Setup at the Originating Endpoint)

[0081] (1)

[0082] The decision to set up a new path is made by AM, triggered by anAM_ALLOCATE_IND from AAL2 control, and based on the implementedthreshold mechanism. AM allocates the resources requested by AAL2control, and determines that the threshold value is exceeded. Hence AMsends an SVC_SETUP_REQ message to the leg controller(LC) of SVC control.The message contains the source and target network element, representedby calling and called party number. These informations are given to AMby AAL2 control, and must be passed on to SVC control to assure that AALtype 2 connections and pathes take the same route through the transportnetwork. Furthermore, the message contains the connectioncharacteristics, which are externally signalled, and which are needed toperform path switching towards the periphery.

[0083] (2)

[0084] The leg controller calls the network routing manager (NRM),providing it at least with the target network element. Certainconnection characteristics, serving as additional route selectioncriteria, and the source network element may be provided as well. NRMreturns a route (an access), which is included into the CMI_SETUPmessage sent to the leg handler.

[0085] (3)

[0086] The leg handler calls AM via SVC_ALLOCATE_IND, delivering theaccess and connection characteristics. AM assigns VPCI, VCI, and pathidentifier, and allocates the resources. LH inserts these data into theCMI_SETUP message to ESIS. Simultaneously, LH issues a connect requestto CRA (see also chapter ‘path switching’).

[0087] (4)

[0088] ESIS encodes the CMI_SETUP into a SETUP message, and sends it viaits protocol handler to the adjacent network element. The arrival of afirst backward message is monitored by a timer (as required by Q.2931).The decoded CONNECT message is passed on to LH.

[0089] (5)

[0090] LH awaits both the confirmation from CRA and the CMI_CONNECTmessage from ESIS, before reporting back to LC.

[0091] (6)

[0092] LC confirms the setup to AM, which now activates the path for thetransport of AAL type 2 connections.

[0093] 0.9.2 Path Setup at the Destination Endpoint

[0094] (FIG. 9: Path Setup at the Destination Endpoint)

[0095] (1)

[0096] ESIS receives a SETUP message from its protocol handler, decodesit, includes the access, and sends a CMI_SETUP to the leg handler of SVCcontrol.

[0097] (2)

[0098] LH calls AM for verification of the path data (VPCI, VCI, pathidentifier). AM reserves the resources in accordance to the requestedconnection characteristics. On positive acknowledgement, LH passes theCMI_SETUP to the leg controller.

[0099] (3)

[0100] LC calls NRM, delivering source and target information,eventually including additional route selection criteria. NRM declaresthat the target has been reached. LC sets up a CMI_CONNECT messagetowards LH, containing an indication that the path is to be terminated.

[0101] (4)

[0102] Interpreting the termination flag, LH calls CRA, and requests theLIC to be connected to an A2SC. After having received the confirmation,LH passes the CMI_CONNECT to ESIS.

[0103] 0.9.3 (5) ESIS Decodes the Message, and Transmits it Over thePreceeding Link

[0104] 0.9.4 Path Release at the Originating Endpoint

[0105] (FIG. 10: Path Release at the Originating Endpoint)

[0106] (1)

[0107] AM deallocates resources for an AAL type 2 connection, and findsout that the path resources fell below the release threshold value. AMcalls the leg controller of SVC control to release an inactive path.

[0108] (2)

[0109] LC sets up a CMI_RELEASE message, and sends it to LH.

[0110] (3)

[0111] LH passes the message to ESIS. Simultaneously, LH issues adisconnect request towards CRA.

[0112] (4)

[0113] ESIS sends a RELEASE message to its succeeding link, receives aRELEASE_COMPLETE message, and transmits a CMI_RELEASE_CNF to LH. TheESIS instance terminates.

[0114] (5)

[0115] LH coordinates the arrival of the disconnect confirmation fromCRA with the arrival of the CMI_RELEASE_CNF message from ESIS. If bothmessages are present, LH calls AM to release VPCI and VCI, (eventuallyalso the path identifier), and to deallocate the resources of the path.If done, LH forwards the CMI_RELEASE_CNF to LC, and terminates.

[0116] (6)

[0117] LC confirms to AM, and terminates. AM releases the pathidentifier (if not yet done on deallocation).

[0118] 0.9.5 Path Release at the Destination Endpoint

[0119] (FIG. 11: Path Release at the Destination Endpoint)

[0120] (1)

[0121] ESIS receives a RELEASE message from its adjacent networkelement, decodes it, and forwards a CMI_RELEASE message to LH.

[0122] (2)

[0123] LH informs LC.

[0124] (3)

[0125] LC reflects a CMI_RELEASE_CNF and terminates.

[0126] (4)

[0127] LH requests disconnection of the path from CRA. On positivereply, LH calls AM for deallocation of the resources. Finally LHacknowledges to ESIS and terminates.

[0128] (5)

[0129] ESIS sends a RELEASE_COMPLETE message over its external link andterminates.

[0130] 0.10 Timers

[0131] ESIS provides timers as required by Q.2931.

[0132] When SVC control is triggered by AM to set up or to release apath, timing is required, and well positioned at the LC instance.

[0133] 0.11 Transit Path Setup

[0134] Considering a path setup at the destination endpoint as shownabove, we let NRM state that the target network element has beenreached. But what to do, if NRM responses with result category ‘routingdestination’, indicating the path to be routed further? Principallythere are three options to react on.

[0135] Option 1: The Single Hop Solution

[0136] SVC control acts as if the routing result ‘local destination’ hasbeen received, that is, the path is terminated within the networkelement. Providing eventually ‘missing path links’ towards the targetnetwork element is left to AM lateron, triggered by AAL2 connectionsetups originating in the given network element.

[0137] Option 2: The Multiple Hop Solution

[0138] SVC control terminates the path within the network element,however continues to setup an outgoing leg. AM, upon receiving a requestfor path resource allocation, now decides to setup another path or not.If AM rejects with an indication ‘Rejected, path available’, SVC controlreleases the outgoing leg, and the job is finished. If AM accepts, SVCcontrol continues to establish the path as usual. As a result, we haveanother path originating in the network element, and either terminatingsomewhere at an intermediate network element, or at the target networkelement.

[0139] Option 3: The Transit Solution

[0140] SVC control does not terminate the path in the network element.Instead, AM is called by the outgoing leg handler to allocate resourcesfor a path, which is the same as the incoming one. Towards theperiphery, SVC control switches through the path in the classical way,that is, from LIC to LIC.

1. Method for transmission of information in paths of an ATM network wherein a path setup for at least one new path in the network is initiated if the path capacity currently used for transmission of information exceeds a threshold (FIG. 14, setup threshold), wherein a path release for at least one path in the network is initiated if the path capacity currently used for transmission of information is below a threshold (FIG. 14, release threshold).
 2. Method according to claim 1 characterized in that the decisions on path setups and/or path releases are made when a new call or an other new data transmission is requested to be set up, wherein preferably for making an anticipatory decision the said capacity currently used for transmission of information includes the capacity necessary for the new call or data transmission.
 3. Method according to any of the preceding claims characterized in that the setup threshold and/or the currently used path capacity represents accumulated cell rates.
 4. Method according to any of the preceding claims characterized in that the thresholds and/or the currently used path capacity represent the number of currently used ATM-channels in one path or in more than one path or in all paths.
 5. Method according to any of the preceding claims characterized in that the thresholds are preset values.
 6. Method according to any of the preceding claims characterized in that the thresholds are variable values that are administrated by the network.
 7. Method according to any of the preceding claims characterized in that the network is an ATM-AAL2 network.
 8. Method according to any of the preceding claims characterized in that the setup threshold exceeds the release threshold.
 9. Method according to any of the preceding claims characterized in that after setup of a path, ATM-channels can be assigned to the path.
 10. Method according to any of the preceding claims characterized in that the path capacity currently used for transmission of information is the current traffic in either one path or all currently used paths.
 11. Method according to any of the preceding claims characterized in that the setup and/or release threshold represents a minimum or maximum of a distance between currently used network resources and all available path resources.
 12. Method according to any of the preceding claims characterized in that a path is an ATM-VCC (ATM virtual channel connection).
 13. Method according to any of the preceding claims characterized in that a channel is an AAL2 channel.
 14. Method according to any of the preceding claims characterized in that after a setup of more than one path, a path is respectively occupied completely with ATM-channels before starting to occupy an other path with ATM channels.
 15. Method according to any of the preceding claims characterized in that a path release for at least one path in the network is initiated only if the path capacity currently used for transmission of information is below a threshold during at least a preset period of time or if it is on the average below a threshold during at least a preset period of time.
 16. Device for transmission of information in paths of an ATM network with means for storing thresholds with means for determining the path capacity currently used for transmission of information with means for comparing the determined path capacity currently used for transmission of information and at least one stored threshold with means (FIG. 10/SVC control; access manager) that are designed for initiating a path setup for at least one new path in the network if the path capacity currently used for transmission of information exceeds a threshold (FIG. 14, setup threshold), with means that are designed for initiating a path release for at least one path in the network if the path capacity currently used for transmission of information is below a threshold (FIG. 14, release threshold).
 17. Device according to claim 16 characterized in that the decisions on path setups and/or path releases are made when a new call or an other data transmission is requested to be set up, wherein preferably the said capacity currently used for transmission of information includes the capacity necessary for the new call or data transmission.
 18. Device according to any of the preceding claims 16-17 characterized in that the thresholds and/or the currently used path capacity represent accumulated cell rates.
 19. Device according to any of the preceding claims 16-18 characterized in that the thresholds and/or the currently used path capacity represent the number of currently used ATM-channels in one path or in more than one path or in all paths.
 20. Device according to any of the preceding claims 16-19 characterized in that the thresholds are preset values.
 21. Device according to any of the preceding claims 16-20 characterized in that the thresholds are variable values that are administrated by the network.
 22. Device according to any of the preceding claims 16-21 characterized in that the network is an ATM-AAL2 network.
 23. Device according to any of the preceding claims 16-22 characterized in that the setup threshold for setup of at least one path is bigger the release threshold for release of at least one path.
 24. Device according to any of the preceding claims 16-23 characterized in that after setup of a path, ATM-channels can be assigned to the path.
 25. Device according to any of the preceding claims 16-24 characterized in that the path capacity currently used for transmission of information is the current traffic.
 26. Device according to any of the preceding claims 16-25 characterized in that the setup and/or release threshold represents a minimum or maximum of a distance between currently used network resources and all available path resources.
 27. Device according to any of the preceding claims 16-26 characterized in that it or a component of it is provided at an access point of an ATM network.
 28. Device according to any of the preceding claims 16-27 characterized in that a path is an ATM-VCC (ATM virtual channel connection).
 29. Device according to any of the preceding claims 16-28 characterized in that a channel is an AAL2 channel.
 30. Device according to any of the preceding claims 16-29 characterized in that after a setup of more than one path, a path is respectively occupied completely with ATM-channels before starting to occupy an other path with ATM channels.
 31. Device according to any of the preceding claims 16-30 characterized in that a path release for at least one path in the network is initiated only if the path capacity currently used for transmission of information is below a threshold during at least a preset period of time or if it is on the average below a threshold during at least a preset period of time. 